Savings for Conditioned Crawlspaces

I'm just getting started with this forum and figuring out where to post these things.

I just posted this question as a blog, but perhaps the "Discussion" format is more appropriate.

I am wondering if anybody out there has run across hard info regarding energy savings from conditioning or encapsulating crawlspaces.

I just finished one and the difference is amazing. Low humidity, very even temperatures and no drafts. It truly does feel like conditioned space.

But how much energy, if any, is it really saving my client? There doesn't seem to be much information on the web about this. But I know that somebody has to have asked this question before me and done a study!

Replies to This Discussion

Great info, Terry. I have had similar experiences. The edge of the slab needs an expansion joint so that the expanding slab in hot weather does not push the foundation apart or buckle. This material is usually compressible so has air in it, and voila - it is an insulator. In fact here they frequently use strips of 1/2" or 3/4" EPS around the edge. That could explain the definite line between cold and warmer.

I'm stuck in the in between world for now, not bad enough for extreme measures and not good enough with a hearing aide to communicate reliably. Poor hearing can be dangerous as the mind can be happy with what it thinks it heard, even though it was wrong. Fortunately, I have found that people are very comfortable in their homes dealing with me as long as we eliminate the background noise. The plus is, you can't find a better way of marketing to people than the personal touch. Since I'm retired, slow is just fine.

Hi Ed. Great point in allowing for expansion and contraction of concrete. I am always pouring against an ICF foam wall. This is easily forgotten about. You have reminded me of a detail that I thought of when desigining the Walden home discussed previously. The homeowner told me she wanted a log cabin and wanted it to be energy efficient and left for back east while we built the home. I've worked on log dog stuff and knew of lots of potential problems, so I decided to make the home look like a log cabin using sidings. So next, I decided to try to do a German style passivhaus for the energy efficientcy. I new little then of the passivhaus standard, but gave it some best guesses. So I decided to do a 16" thick double 2x4 wall system with 2.5" of eps foam on the outside. The foundation was to be my usual ICF Amvic forms and I typically cut off the inside top of the form down 4" to allow the concrete slab with radiant tubing to abutt the 2.5" exterior ICF foam. It has a wimpy R value of 10. so I realized that I could add more foam to the inside and not cut off the inside top foam of the ICF because of my big wide wall. I actually added two layers of 2.5" eps foam to the inside edge of the top of the wall. The top of the ICF wall was poured level with the top of the slab. So now I have an R of 40 for my slab perrimeter. The walls were dense packed cellulose and had an R of 65 to 70. The home's roof system is parellel cord trusses 16" deep with 2.5" foam on top of roof sheathing, then 2x4 24" on center for steel roofing attachment. Another R of 70. The underslab foam was eps of 7.5" for an R of 30. Windows were tripane Gienow's from Canada. I then did the usual energy recovery ventilator, but decided to heat the place with an electric water heater using 85% power from big dams on the Columbia river. I also installed 4 Viessmann flat plate solar thermal collectors on the roof and used a 119 gallon tank to store the energy from the sun. Then, when the home needs heat it turns a pump on and exchanges heat via a flat plate heat exchanger to the radiant floors. Last winter we had not much sun and a lot of snow. I figured the system was not working much on collecting energy but the home still had a yearly heat bill of 125 dollars. Now I want to tie in ground source heat pumps to my solar. So much for the simple way of building. The homeowners do not know how to live in this home yet. They think they need to burn wood, after all it's a log home, Right? They soon ran themselfs out of the building as they installed a big ol' wood stove, with outside air, of course.

I just wanted to share my discovery of thicker walls equals more foam for slab perrimeter insulation. Thanks for the reminder and keep up the great work!

Mistakes that I made on this home were; Not using a 90 plus percent HRV instead of the 70% ERV, not using 5 or 6 solar collectors intead of four, and not using a better solar heat gain on the south windows. and not explaing or writing an owners manual of how to live in the home. allowing a clothes dryer to be installed instead of a drying rack vented out through the ventilator. Not venting the kitchen cooktop and using a grease filter instead.

Congratulations - that is an admirable hea tbill in Montana. A couple of questions: How big is the house? How many Degree Days in your area? What do you pay for Columbia River electricity? What was the blower door number. And most important, and this is hard to quantify, how much extra over a conventional code house did the construction cost - best guess? And last - what would the heat bill of the code house be using electric to heat - again, best guess.

I think the house is 1200 ft2 on the inside and since the wall wound up 22" thick, it is 1400 ft2 on the outside. Hamilton MT is around 7700 heat degreee days. The Ravalli Electric Co Op used to cost 5.3 cents, but last month (July 2011) it went up to 8.8 cents a KWH. So, for the data, it is the 5.3 cents. The blower door number was 0.49 ACH50. to insulate the place,( for the cellulose) cost $10,000. the eps rigid foam cost 4,000 dollars. The solar thermal cost $14,000. The home wound up costing around $220,000. or $157 per ft2. I do a lot of the sub trade work myself, in house, so I save on the profits that the subs normally charge. I would guess the code built homes' heat bill would be 800 to 1000 dollars per year for our climate.

We have a saying; "When summer comes to Montana, sure hope that it falls on the weekend"! You can see this house and others on my website, www.naturalhousebuilder.net Thanks!

I have been all excited to measure ground temperature in the last couple a' days. My Caleffi idronics came in the mail, and it is on heat pumps. So I found my old notes, and on Dec. 31, 2010, I measured my well water temperature. the well is 40 ft deep and the outside temp was 10f. the water temp was 50F. I measured the well the other day, I think the outside temp was close to 90F and the well water temperature was 60F. I think our water here would foul the ground source heat pumps heat exchanger in using the well water for the heat source. I'm gona do ground loops with manifolds.